The present type of device conventionally provides only an original document cover C which can be opened and closed so as to hold down an original document B disposed upon an original document platen A when in the closed position covering said document platen A, as shown in FIG. 1.
Furthermore, when original document B is a diagram which exceeds the JIS A2-size paper it often bears a distinct crease on the corner or edge of the interior face, or it possesses a distinct curl due to being lightly rolled into a cylindrical shape for storage.
When original documents of these types are copied, the original document B is lifted up by the fold, curl or the like at an imaginary line as shown in FIG. 5 even if held down by the aforesaid document cover C. Further, when said document cover C is simply pressed, a backward warp is induced toward the inside of the document without spreading flat and pinning the aforesaid fold or curl, thereby damaging the original image while imparting a fold thereto.
Thus, two persons must act cooperatively so that one person presses down the lifted portion of document B with his hands, while another person closes document cover C.
When a separate document cover D is used in addition to document cover C, said cover D must first be pressed on the portion of document B to be copied, as shown in the drawing, then document cover C is closed on said cover D and the copying operation is performed. However, this operation requires additional components and complicates the entire process.
It is known that devices eliminating these disadvantages are disclosed in Japanese Pat. Nos. Sho 59-141341 and Sho 6028756. These devices are provided with a notch in a portion of the elastic member which forms the surface of the original document cover, and have a rotatable document pressing member disposed in said notch so as to have the document pressing member clamp down on the original document disposed on the document platen when the document cover is closed. Thus, even original documents which are bent backward due to permanent creases or curls can be pressed to the document platen by simply closing the document cover.
However, the document pressing member remains positioned behind the original document even after the completion of the pressing action, because the aforesaid document pressing member stays in the pressing attitude after the document cover is closed. Therefore, when a thin sheet or transparency such as tracing paper is used, an image or shadow formed by the notch on the elastic member of the document cover, document pressing member and its support member may appear in the copy image.
Furthermore, because the document pressing member can only be provided to a limited portion of the document cover surface, it can only press a limited portion of the original document disposed upon the document platen. Therefore, said device is inadequate and ineffective on the edges of original documents which are easily folded backward.